In general, elastic members such as weather strips are made of either thermoplastic resin such as PVC containing plasticizer or thermosetting resin known as synthetic vulcanized rubber such as EPDM and SBR.
In some of these long elastic members, each of them is modified in cross section to conform to the configuration of a clearance around a vehicle door or to prevent deformation resulting from buckling at corner sections thereof. Methods of manufacturing such members are described in, for example, Japanese Laid-Open Utility Model Publications Nos. 1-152854 and 1-152856, Japanese Patent Publication No. 59-182722.
Each of the methods disclosed in the above described publications is performed by using an extrusion molding die having a shaping member which is movably mounted in an extrusion opening of the die, in which the shaping member, when an extrusion molded article as the elastic member is extruded from the extrusion opening, is moved toward or away from the extrusion molded article, thereby permitting modification of the cross-sectional configuration of the extrusion molded article.
As described above, in the conventional method in which the shaping member, when an extrusion molded article is extruded from the extrusion opening, is moved toward or away from the extrusion molded article so as to modify the cross-sectional configuration of the extrusion molded article, the extrusion molded article is usually cooled immediately after being passed through the die if the thermoplastic resin is used. Therefore, the molded article is cooled while the configuration as shaped by the shaping member is still maintained. This may form the long elastic member having a desired cross-sectional configuration.
On the other hand, where the extrusion molded article is formed of the synthetic vulcanized rubber such as EPDM, a synthetic vulcanized rubber material exhibits claylike plastic property since it does not have elasticity unless vulcanization treatment is applied thereto. Generally, since the vulcanization treatment can not be sufficiently performed by utilizing a short bath such as a cooling bath for the thermoplastic resin extrusion molded article, the vulcanization treatment is carried out by utilizing a vulcanizing bath having a length of from several tens of meters to hundreds of meters. As should be apparent, a vulcanizing reaction to the synthetic vulcanized rubber has not yet occurred at the vicinity of an inlet of the vulcanizing bath. When the extrusion molded article extruded at temperatures of 100.degree. C. or below is introduced into the vulcanizing bath kept at temperatures of 180.degree. C.-220.degree. C., viscosity of the article is usually temporarily reduced immediately thereafter, and the vulcanizing reaction mainly progresses at an area from the front half toward the middle of the bath.
Therefore, to obtain the molded article having a desired cross-sectional configuration, the cross-sectional configuration of the extrusion molded article has to be sustained to a desired configuration at a position in which the synthetic rubber is in a "semi-vulcanized state", that is, in a state where the vulcanizing reaction is gradually started.
In a case where the extrusion molded article is shaped to the desired cross-sectional configuration by utilizing the shaping member, immediately after being passed through the die as in the conventional technique, the extrusion molded article has to be stably transferred to the middle of the vulcanizing bath, with its condition maintained.
However, in order to accurately harmonize extrusion speed of the extrusion molded article extruded from the die, moving speed of a conveyor for transferring the extruded article and pulling speed of a pulling machine, it is required to take various measures, for example, to substantially increase accuracy of each machine and to additionally provide equipment for harmonization. This may lead to increased investment. Moreover, since extrusion conditions usually vary with changes in ambient temperature, variations in properties of a molding material between lots, and other factors, it is substantially difficult to accurately harmonize such speeds. Also, due to inevitable factors such as vibrations in a factory, the shaped configuration of the extrusion molded article can not be kept and is deformed to an awkward configuration.